<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8" />
  <meta http-equiv="X-UA-Compatible" content="IE=edge" />
  <meta name="viewport" content="width=device-width, initial-scale=1.0" />
  <link rel="stylesheet" href="./css/index.css" />
  <title>记事本</title>
</head>

<body>

  <!-- 主体区域 -->
  <section id="app">
    <!-- 输入框 -->
    <header class="header">
      <h1>小黑记事本</h1>
      <input v-model="num" placeholder="请输入任务" class="new-todo" />
      <button @click="add" class="add">添加任务</button>
    </header>
    <!-- 列表区域 -->
    <section class="main">
      <ul class="todo-list">
        <!-- <li class="todo">
          <div class="view">
            <span class="index">1.</span> <label>吃饭饭</label>
            <button class="destroy"></button>
          </div>
        </li> -->
        <li v-for="(item,index) in list" class="todo">
          <div class="view">
            <!-- <span class="index">{{index+1}}</span> <label>{{item.age}}</label> -->
            <span class="index">{{index+1}}</span> <label>{{item.age}}</label>
            <button @click="del(index)" class="destroy"></button>
          </div>
        </li>
      </ul>
    </section>
    <!-- 统计和清空 -->
    <footer class="footer">
      <!-- 统计 -->
      <span class="todo-count">合 计:<strong> {{list.length}} </strong></span>
      <!-- 清空 -->
      <button @click="clear" class="clear-completed">
        清空任务
      </button>
    </footer>
  </section>

  <!-- 底部 -->
  <script src="https://cdn.jsdelivr.net/npm/vue/dist/vue.js"></script>
  <script>

    const app = new Vue({
      el: '#app',
      data: {
        list: [
        ],
        num: ''
      },
      methods: {
        del(index) {
          this.list.splice(index, 1) //删除，根据索引删除
        },
        add() {
          let num = this.list.length //获取数组长度
          //this.list.push({ id: num === 0 ? 1 : this.list[num - 1].id + 1, age: this.num })//向数组插入对象
          //注意：此处需要判断数组是否为空，如为空，则id需要手动赋值为0（三元运算符通过数组长度判断）

          this.list.unshift({ id: num === 0 ? 1 : this.list[num - 1].id + 1, age: this.num })
          this.num = '' //清空
        },
        clear() {
          this.list.splice(0)
        }

      }
    })

  </script>
</body>

</html>